The importance of trust as a key facilitator of electronic commerce is increasingly being recognized in academic and practitioner communities. However, empirical research in this area has been beset by conflicting conceptualizations of the trust construct, inadequate attention to its underlying dimensions, causes, and effects, and lack of a validated trust scale. This paper addresses these limitations in part by theoretically conceptualizing and empirically validating a scale to measure individual trust in online firms. The proposed scale taps into three key dimensions of trust: trustee's ability, benevolence, and integrity. An iterative testing and refinement procedure using two field surveys of online retailing and online banking users, leads to a final seven-item trust scale that exhibits adequate levels of reliability, convergent validity, discriminant validity, and nomological validity. It is expected that the scale presented in this paper will assist future empirical research on trust in online entities.